1. Field of the Invention
This invention pertains to the fields of ammunition and explosive devices. More particularly, this invention pertains to fuses, primers and igniting devices. In still greater particularlty, this invention pertains to a safe-arm device for use with a missile warhead. By way of further characterization and explanation, this invention pertains to a safe-arm device utilizing a solenoid which allows axial and rotational movement of a rotor based on predetermined signals.
2. Description of the Prior Art
The explosive material used in warheads is basically insensitive to shock, vibration, temperature and static electricity. This makes the material safe to handle but also difficult to detonate at the desired time. To cause warhead detonation, a warhead initiation system and explosive train are required. The safe-arm explosive train consists basically of a detonator, explosive leads and an explosive booster or warhead initiation system. The detonator is very sensitive to all elements and is fired by electric energy from the firing circuit. Its explosive output, which is small, then detonates the explosive lead and the explosive lead in turn the explosive booster. The function of the safe-arm is to physically and electrically isolate the detonator from the rest of the explosive train until arming occurs. The warhead initiation system distributes the explosive detonation wave to the proper points of the warhead. For simple isotropic warheads, a sophisticated initiation system is not needed since only a single point of the warhead is detonated.
A directed warhead, such as that shown in U.S. Pat. No. 3,714,897 issued to L. L. Parker on Feb. 6, 1973, requires a safety-arming device capable of processing multi-channel information. The safety-arming device receives a number of signals from the target detecting device and it signals the directed warhead to deform and then detonate in a specified direction. Such a warhead would require a number of explosive leads because the warhead detonation may be in any direction. Prior art devices are limited in the number of explosive leads which they may contain. Because of their complicated nature and size and weight considerations, the devices could not be used where a number of explosive leads are required.
In general, a safety-arm device achieves its safety with barriers in the explosive train that are removed sequentially after missile launch. The final barrier is removed after a safe separation point with respect to the launch medium has been reached. This safe separation point is established through analysis that takes into account such factors as missile debris due to warhead detonation, missile trajectories and the probability of a fragment hit on the launching platform. The safe separation point is typically either a single time or distance with respect to the launching medium. For most rocket motor boosted missiles, distance is used as the criterion for safe separation. When safe separation is achieved, the barriers from the explosive train are removed and the detonator is electrically armed. The explosive train will then be ready to detonate the warhead with the receipt of a signal from either the target detecting device or contact fuse.
Prior safety-arming devices have used an escapement (integrator) for safe arming. One such device is shown in U.S. Pat. No. 3,776,138 issued to S. A. Moses on Dec. 4, 1973. In that device, the detonators are separated from detonating fuses by a rotating, cylindrical shield. The escapement causes the shield to rotate upon acceleration thereby aligning the detonators and fuses. While suited for its intended purpose, the escapement depends only upon acceleration of the missile to arm the warhead. To meet modern fuze safety criteria, a more reliable device with fewer components which utilizes two independent signals to arm the warhead is required.